In diesel fuel injection systems of the type wherein a high pressure pump periodically supplies a quantity of fuel to an injector nozzle for injection into the cylinder of an engine, flow from such an injector nozzle is normally controlled by a pressure actuated valve, which may be either of the outwardly or inwardly opening type, with this valve being conventionally spring biased to its closed position.
Fuel injection nozzles having an inwardly opening valve normally utilize a differential area type valve therein and as such this type nozzle usually requires a drain conduit to be connected thereto for use in draining off any fuel which has leaked between cooperating elements of the valve assembly in such a nozzle. This is due to the fact that in this type nozzle arrangement, the nozzle assembly must be constructed so as to provide a low pressure chamber into which the stem of the valve extends in order to provide for the necessary pressure differential required to act on the valve to effect opening movement thereof against the closing bias of the conventional spring used to effect closing movement of the valve.
To eliminate the need for such a drain conduit in this type fuel injector nozzle, it has been previously proposed to provide in such a nozzle assembly an accumulator chamber into which fuel leakage can flow. However, such a fuel injection nozzle, with an accumulator chamber therein, may operate in an erratic manner due to the fact that, as the pressure of fuel gradually builds-up in the accumulator chamber due to continuous leakage of fuel past the cooperating elements of the valve assembly, the actual pressure differential pressure acting on the valve to effect valve opening movement will gradually decrease due to this buildup of pressure in the accumulator chamber and thus affects the nozzle opening pressure causing injection distribution errors. It will be apparent that, as this pressure in the accumulator chamber increases up to a value corresponding to that of the fuel being supplied by a pump to the injection nozzle, a hydraulic block can occur, which of course may prevent the injection valve from opening.